: The currently accepted theory for the Moon's formation is that it was produced by the collision of a Mars-sized object with Earth. As a result, the early Moon had a molten core and a magnetic field. Evidence of that magnetic field would be stored in lunar rocks as they cooled. Two low-flying lunar orbiters—Lunar Prospector
—mapped local magnetic fields, and now a team of Japanese researchers has used those maps to calculate the orientation of the magnetic field at various points in time. Most of the data points aligned with the current pole, but a distinct set of points were oriented between 45° and 60° away from the current pole. The finding suggests that the magnetic field, and probably the entire Moon itself, experienced a sudden jump in orientation at some point in the past. The researchers suggest the jump could have been caused by a major impact, internal instabilities, or the gravitational effect of the movements of other planets in the solar system. The data lack the precision necessary to determine when the reorientation occurred, but other evidence has previously hinted at such an event.